Breakdown in decision making and propensity for risk taking are common features of drug addiction that contribute in part to increased rates of unsafe sexual and drug using practices. Compelling evidence demonstrates that HIV+ drug users are more vulnerable to decision making defects. However, there are essentially no studies of the integrity of decision making among drug-using HIV+ men who have sex with men (MSMs), whose patterns and context of drug abuse and sexual risk taking are substantially different from the crack or opiate-dependent participants of previous studies. We propose a two year feasibility study of neurocognitive aspects of decision making among a sample of participants from the Chicago MACS cohort. This site-specific pilot study will address the feasibility and scientific utility of: 1) characterizing the integrity of decision making among drug using participants enrolled in the Chicago MACS;2) comparing the performance of drug-using HIV+ with HIV- MACS participants and 3) obtaining preliminary data regarding potential associations between performance on these measures with high risk sexual and drug use behavior. Models of impaired decision making in neuroAIDS have clear translational potential for the design of more specific interventions for risk prevention and substance abuse treatment among MSMs. People with HIV/AIDS are living longer since the introduction of potent antiretroviral therapies but HIV still affects the brain and can impair memory and other cognitive functions. A history of drug abuse may increase the risk of HIV-associated neurocognitive impairment;in particular, it appears that both HIV and drug abuse can affect a person's ability to make safe decisions in risky situations. This pilot project in Chicago will evaluate how well MACS participants who have used drugs can make safe decisions and whether this will predict subsequent risky sexual activity and drug use. The information gathered in this project may be able to help us develop more specific prevention methods and substance abuse treatments.